In the fabrication of semiconductor devices, a thin passive layer of a chemically inert dielectric material such as, silicon nitride (Si3N4) or silicon carbo-nitride (SixCyNz) is essential. Thin layers of silicon nitride function as diffusion masks, oxidation barriers, trench isolation, intermetallic dielectric material with high dielectric breakdown voltages and passivation layers. Many applications for silicon nitride coatings in the fabrication of semiconductor devices are reported elsewhere, see Semiconductor and Process technology handbook, edited by Gary E. McGuire, Noyes Publication, New Jersey, (1988), pp 289-301; and Silicon Processing for the VLSI ERA, Wolf, Stanley, and Talbert, Richard N., Lattice Press, Sunset Beach, Calif. (1990), pp 20-22, 327-330.
Many of the new semiconductor devices require dielectric films that have very low etch rates or very high film stresses, or both. It is also preferred, and sometimes necessary, that the films be formed at temperatures below 600° C. while maintaining good electrical characteristics. Film hardness is another factor to consider in the design of the electrical components and the silicon nitride films do offer extremely hard films.
One of the commercial methods for forming silicon nitride coatings employs dichlorosilane and ammonia as the precursor reactants. Low pressure chemical vapor deposition (LPCVD) using precursors such as dichlorosilane and ammonia require high deposition temperatures to get the best film properties. For example, temperatures greater than 750° C. may be required to obtain reasonable growth rates and uniformities. Other processing issues involve the hazardous aspects of chlorine and chlorine byproducts.
The following articles and patents are cited as representative of the art with respect to the synthesis of organosilanes and deposition processes employed in the electronics industry.
A. K. Hochberg and D. L. O'Meara, Diethylsilane as a Silicon Source for the Deposition of Silicon Nitride and Silicon Oxynitride Films By LPCVD, Mat. Res. Soc. Symp. Proc., Vol. 204, (1991), pp 509-514, disclose the formation of silicon nitride and silicon oxynitride films using diethylsilane with ammonia and nitric oxide by LPCVD. The deposition is carried out in a temperature range of 650° C. to 700° C. The deposition is limited generally to a temperature of 650° C. as the deposition rate drops to below 4 ANG./min at lower temperatures.
Sorita et al., Mass Spectrometric and Kinetic Study of Low-Pressure Chemical Vapor Deposition of Si3N4 Thin Films From SiH2Cl2 and NH3, J. Electro. Chem. Soc., Vol. 141, No. 12, (1994), pp 3505-3511, describe the deposition of silicon nitride using dichlorosilane and ammonia using a LPCVD process. The formation of ammonium chloride leads to particle formation and deposition of ammonium chloride at the backend of the tube and in the plumbing lines and the pumping system.
Aylett and Emsley, The Preparation and Properties of Dimethylamino and Diethylamino Silane, J. Chem. Soc. (A) p 652-655, 1967, disclose the preparation of dimethylamino and diethylaminosilane by the reaction of iodosilane with the respective dialkyl amine.
Anderson and Rankin, Isopropyldisilylamine and Disilyl-t-butylamine: Preparation, Spectroscopic Properties, and Molecular Structure in the Gas Phase, Determined by Electron Diffraction, J. Chem. Soc. Dalton Trans., p 779-783 1989 disclose the synthesis of disilyl amines of the formula NR(SiH3)2, e.g., isopropyldisilylamine and disilyl-t-butylamine and they provide spectroscopic comparisons to the corresponding methyldisilylamine.
Japanese Patent 6-132284 describes the formation of silicon nitride films using organosilanes having a general formula (R1R2N)nSiH4-n, (where R1 and R2 range from H—CH3—, C2H5—C3H7—, C4H9—) by either a plasma enhanced chemical vapor deposition or thermal chemical vapor deposition in the presence of ammonia or nitrogen.
U.S. Pat. No. 5,234,869 discloses the formation of a silicon nitride film by CVD using Si(N(CH3)2)4 and ammonia as reactant gases. A chamber temperature of 700° C. and a pressure of 0.5 Torr was used for the deposition. Other reactants selected from the group consisting of SiH(N(CH3)2)3, SiH2(N(CH3)2)2, and SiH3(N(CH3)2) in combination with ammonia or nitrogen were also suggested as reactants. It was also disclosed that plasma produced by radiating the gas with an ultra-violet beam, the temperature was decreased to 300° C.
U.S. Pat. No. 5,874,368 teaches the use of bis(tertiarybutylamino)silane as a precursor to deposit silicon nitride using low pressure chemical vapor deposition at a temperature range of 500° to 800° C.
U.S. Pat. No. 5,874,368 and U.S. Pat. No. 6,153,261 disclose the formation of silicon nitride films using bis(tertiarybutylamino)silane as a silicon reactant gas. LPCVD is used to generate the film.
U.S. Pat. No. 6,391,803 discloses the formation of silicon containing thin films by atomic layer deposition using a silane of the formula Si(N(CH3)2)4, SiH(N(CH3)2)3 SiH2(N(CH3)2)2 SiH3(N(CH3)2), preferably trisdimethylaminosilane, as a first reactant. A portion of the first reactant is chemisorbed onto the substrate and a second portion is physisorbed onto the substrate. The reactant is purged and a second reactant, i.e., NH3 is introduced.